diff options
Diffstat (limited to 'pod/perlfunc.pod')
| -rw-r--r-- | pod/perlfunc.pod | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index d730b43e47..dbefd85ee4 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -1422,8 +1422,16 @@ element is not autovivified if it doesn't exist. A hash or array element can be true only if it's defined, and defined if it exists, but the reverse doesn't necessarily hold true. +Given an expression that specifies the name of a subroutine, +returns true if the specified subroutine has ever been declared, even +if it is undefined. Mentioning a subroutine name for exists or defined +does not count as declaring it. + + print "Exists\n" if exists &subroutine; + print "Defined\n" if defined &subroutine; + Note that the EXPR can be arbitrarily complicated as long as the final -operation is a hash or array key lookup: +operation is a hash or array key lookup or subroutine name: if (exists $ref->{A}->{B}->{$key}) { } if (exists $hash{A}{B}{$key}) { } @@ -1431,6 +1439,8 @@ operation is a hash or array key lookup: if (exists $ref->{A}->{B}->[$ix]) { } if (exists $hash{A}{B}[$ix]) { } + if (exists &{$ref->{A}{B}{$key}}) { } + Although the deepest nested array or hash will not spring into existence just because its existence was tested, any intervening ones will. Thus C<$ref-E<gt>{"A"}> and C<$ref-E<gt>{"A"}-E<gt>{"B"}> will spring @@ -1448,6 +1458,12 @@ release. See L<perlref/"Pseudo-hashes"> for specifics on how exists() acts when used on a pseudo-hash. +Use of a subroutine call, rather than a subroutine name, as an argument +to exists() is an error. + + exists ⊂ # OK + exists &sub(); # Error + =item exit EXPR Evaluates EXPR and exits immediately with that value. Example: |